In the preparation of commercial hydrocarbon product, it is often necessary to separate the desired product from other hydrocarbons having similar boiling points. For example, butene is synthesized commercially by processes which yield butadiene mixed with 1-butene. Conversely, butadiene product may also be contaminated with butene. Depending on the process used, the mixture may include other C.sub.3 and C.sub.4 hydrocarbon components including but not limited to 2-butene, other n-butenes, n-butane, isobutane, and isobutylene.
Purifying the mono-olefin, 1-butene, is particularly troublesome due to the closeness of its boiling point to that of 1,3-butadiene. In order to increase the purity of 1-butene, it is necessary to separate it from other hydrocarbons. Ordinarily, fractionation alone is incapable of completely separating 1,3-butadiene to achieve the desired purity of 1-butene in these mixtures. Presently, butadiene is separated from olefins and paraffins primarily by distillation with selective solvents and by absorption using solutions of absorbents. Extractive distillation is relatively energy-intensive, complex and not economical. Selective absorption with metal salt solution involves a significant number of stages with recycling of streams between stages. This method has the disadvantage of being energy-intensive and requiring handling and recirculating of solvent streams which themselves contain contaminants or are subject to degradation. Current processes for olefin/paraffin separation have not been sufficiently selective to economically achieve the desired result for purifying mixtures of unsaturated hydrocarbons. Therefore, there remains the need for an improved method and improved adsorbents for use in methods to effectively and economically purify unsaturated hydrocarbons.